Method for the manufacture of screens



P 1932. r I I J. HEIDENHAIN 1,877,310

METHOD FOR THE MANUFACTURE OF SCREENS Filed July 9, 1930 fizifles y: I 72;Venf0r: gym 2. I 70 Ha ud w Patented Sept. 13, 1932 UNITED STATES PATENT OFFICE JOHANKES HEIDENHAIN, OF BERLIN, GERMANY METHOD non diam MANUFACTURE or SCREENS Application filed July 9, 1930,1 Serial No. 466,892, and in Germany August 10, 1929.

This invention relates to a method for the manufacture of screens.

.More particularly it relates to a process of manufacturing screens for photo-chemical and photo-mechanical reproductions.

I Heretofore in the manufacture of a screen for such reproductions, the lines for the screen had to be drawn on a dividing machine, which is an expensive item to be considered in relation to the selling costs of the resultant product.

It is one object of my invention to obviate the use of expensive dividing machines-and the expensive work heretofore necessary in the use of such machines for manufacturing screens with drawn lines thereon.

Another object of my invention is to pro vide a simple and comparatively inexpensive method of manufacturing screens.

With the above and other objects in view, the invention in its preferred form consists of a method whereby a transparent plate is coated to form a mirror and the resultant coating on the plate is made light sensitive. 5 The plate is then provided with an original negative having certain portions imperviou's to light and which is then exposed to the action of light, whereupon a design is effected on the plate by means of copying in the usual photographic way. The plate film is then etched.

. Referring in detail to the drawing, wherein 'I have shown one simple and practical embodiment of the invention, and in which similar reference characters designate. cor

responding parts throughout the severalsake of illustration and clarity shows the.

various steps of the invention in its pre- 5 ferred form, smooth faced transparent plate 1, made of glass, celluloid, or other transparent material, is considered as the screen to contain material on to which a design, or the like, is to be impressed. Onto the smooth face of the plate a film or layer 2, of lead sulphide is formed to provide a lead sulphide mirror.

By way of illustrating my preferred manner in which the lead sulphide. mirror is formed on plate 1, equal quantities of solue0 tions of lead acetate, thiourea and caustic potash are mixed together. Each solution has a strength of 2% of active material therein, and is prepared with distilled water to avoid contamination. in the preparation of plate 1, the solutions are quickly mixed together in the order above noted, and the plate 1, is quickly dippedinto the liquid mass; The solution is gently heated to aid precipitation of the resultant lead sulphide on the plate 1. While the heating is continued the plate is kept incontact with solu tion until a film or layer of lead sulphide of the desired thickness for density is attained. The resultant layer of lead sulphide forms a mirror which adheres very firmly to the smooth face of the plate 1. To the layer 2, of the lead sulphide mirror adhering to the smooth face of plate 1, alight sensitive layer 3 of albumin-ammonium bichromate is added.

The last added layer is allowed to dry whereupon an original negative plate 4-, is placed over the film. The original negative plate 4, consists of lines or points impervious to light. The negative plate 4, is then placed over the layer 3, of plate 1, and held firmly in position The plate 1, is then exposed to photochemical action whereupon the light used passes through the open portions of the 90 plate 4, onto the layer 3, to produce thereon the outline according to the general design of the original screening plate 4. The negative 4 allows for the formation of clean cut markings on the layer 3, thereby enabling the i a.) resultant screen to have clear lines when etched, as will be hereinafter described. The design on the negative plate 4, maybe of any kind and must correspond to the requirements of the screen to be manufactured. 1 0

When the film on plate 1, has been thus marked off to correspond with the negative plate, the film layer 3, is treated with an ink color or paint and developed by washing with Water so as to dissolve the water soluble or unexposed parts of the layer The plate is dried and then prepared by covering the ink carrying spaces with an acid-proof substance, for example, asphalt. The layers of the plate are then etched by dipping the plate into anetcliing solution, such asferric chloride. When the etching action ofthe ferric'chloride is complete, plate 1, is removed from the etching solution and washed free of any iron chloride sticking to the plate. The asphalt ink layer on the plate is then removed by means of ben zine, or any other commonly used solvent.

While my invention has been described as referring to the manufacture of screens on plates of glass, celluloid or the like, it is to be noted that it is also adapted for intaglio printing. Furthermore, the printing of the picture canbe performed on anytype of a sensitive transparent plate such as have parallel' lines, criss-cross lines, or as have a grained appearance due to the opaque pitted or dotted sections on the plate or vice versa. While the invention has been described in its preferred form, it is to be noted that vari ous changes or modifications as to form, size, and obvious expedients may be made without departing from the spirit and scope of my invention as defined in the herein appended claims. a

Having described the invention, what I claim is: I

1. In the method of manufacturing screens the steps consisting of dipping smooth faced transparent material into an aqueous solution of lead acetate, thiourea, and caustic soda,

warming the solution containing the plate to the films of the plate with a negative screen to cover certain portions of the film, subjecting the film to photochemical action to obtain impressions on said film corresponding to those of the negative, then developing. the

film,'washing out the unexposed parts of said film, and then finally etching the plate.

4 2. In the method of manufacturing screens, the steps consisting of coating a transparent plate with a film of lead sulphide, coating said film with an emulsion of optically sensitive material, drying the resulting'layer, covering plate with a film of lead. sulphide, coating said film with an emulsion of optically sensi-. tive material, drying the resulting layer, covering it with a negative screen to form fields and lines thereon, subjecting the film to photochemical action to obtain impressions thereon corresponding to those of the negative, developing, washing out the unexposed parts of the layer, drying the plate and coating with an ink color, covering the ink carrying spaces with an acid proof substance and then'etching the plate by dipping in a solution of ferric chloride.

In testimony that'I claim the foregoing as my invention, I have signed my name here- J OHANNES HEIDENHAIN.

it with a negative screen to form fields and I lines thereon, subjecting the film to photochemical action to obtain impressions thereon corresponding to those of the negative, developing, yvashing out the unexposed parts of tlielayer, drying the plate and then etching 

